South Korea on Wednesday warned North Korea not to conduct a nuclear weapons test, saying it would further isolate the communist regime, while countries launched new efforts to persuade the North to resume stalled disarmament talks.
South Korea's Foreign Minister Ban Ki-moon said a nuclear test by North Korea would be much more serious than its July missile tests and create a "threatening situation that will shake the foundation of the global nonproliferation system and will further isolate the North."
Ban said a North Korean nuclear test was a possibility and that Seoul needs more specific information. He added that the South was sharing information with other countries and keeping a close watch on the North.
Concerns about a possible North Korean nuclear test grew after an ABC News report last week cited U.S. officials as saying that potentially suspicious activity had been observed at a suspected underground nuclear test site.
South Korea's military has said it sent personnel to keep a round-the-clock watch at a seismic monitoring station to detect tremors that could indicate a nuclear explosion.
North Korea's missile tests last month raised regional tensions and prompted U.N. Security Council sanctions against the North.
North Korea has claimed it has nuclear weapons, but hasn't performed any known test to confirm it has successfully manufactured an atomic bomb. However, many experts believe the North has enough radioactive material to build at least a half dozen or more nuclear weapons.
Talks on North Korea's nuclear program have been deadlocked since November, when negotiators failed to make headway in implementing a September agreement in which North Korea agreed to give up its nuclear program in exchange for aid and security guarantees.
North Korea has since refused to attend six-nation talks on its nuclear program until Washington stops blacklisting a bank where the communist regime held accounts, a restriction imposed over alleged counterfeiting and money laundering.
Trying to break the impasse, South Korean presidential security adviser Song Min-soon will make a two-day trip to China starting Thursday for talks with Chinese Foreign Minister Li Zhaoxing and other officials.
Japan's top nuclear envoy, Kenichiro Sasae, arrived Wednesday in Seoul for similar consultations with his South Korean counterpart, Chun Yung-woo, and other officials.
Washington has called on the North to return to the nuclear talks without conditions, saying the issue is unrelated to the financial restrictions. The talks involve the two Koreas, China, Japan, Russia and the U.S.
Meanwhile, North Korea insisted Wednesday it posed no threat to the South and condemned ongoing U.S.-South Korea joint military drills as a prelude to war.
"There are no forces of war threatening South Korea in the Korean Peninsula at present," the North's main newspaper, Rodong Sinmun, wrote in a commentary carried by the official Korean Central News Agency.
Seoul and Washington have said the exercises — mostly simulation-driven drills that run through Sept. 1 and involve some 17,000 troops — are defensive in nature.